The present invention relates generally to cementing compositions and slurries that are useful for water control in oil and gas wells, and methods of using them to terminate water flow in subterranean formations.
In the operation of wells used in the recovery of fluids from or the introduction of fluids into subterranean formations, problems relating to the unwanted passage of water from undesirable locations in the formation or well bore sometimes occur. This unwanted passage of water can severely disrupt or in fact terminate the desired operation of a well.
To be more specific, the problems ordinarily involve the movement of water through very small undesirable openings. These problems are not unique, and solutions have traditionally involved apparatus, methods and compositions adapted to cover, seal or to otherwise plug the openings to thereby terminate the unwanted passage of fluid therethrough. The openings include holes or cracks in well casing; spaces such as holes, cracks, voids or channels in the cement sheath deposited in the annular space between the formation face and well casing; very small spaces called microannuli between the cement sheath, and the exterior surface of the well casing or formation; and permeable spaces in gravel packs and formations.
Still another problem involved in the operation of wells revolves around the unwanted movement of water via cracks and fractures in the subterranean formation—whether naturally occurring or deliberately produced—from the formation into the well bore. Terminating this water movement may require remedial efforts other than those referred to above that typically involve plugging perforations, holes, cracks and the like in casing, cement sheath and gravel packs—all of which occur within the confines of the well borehole itself.
Conventional substances used in sealing or plugging the holes or cracks have included diesel oil cements that include an API Class cement, a surface-active agent and diesel oil or kerosene. These diesel oil type cements do not set until they are placed in a water-bearing zone where they absorb water and set. Many of these cements take considerable time to set and develop strength. Thus, there is a need for improved compositions and methods that provide rapid-setting and strong materials in a short period of time.